Substation circuit



Patented 21, 1933 UNETED STATES LABORATORIES, INCORPORATED, YORK PATENTGFFlCE JOHN W. GOODERHAII, OF LABGEMONT, NEW YORK, ASSIGNGB '10 BELLTELEPHONE OF NEW YORK, N. Y. A CQEPOBATION OF NEW sunsrnrron orreocrrApplication area name a, rear Serial 251e, erases.

This invention relates to circuit arrange ments for signaling systemswherein signals may be transmitted from or received at the same station.More specifically, this invention is embodied in a subscribers telephonestation or substation, as it is more commonly called, and moreparticularly in the combination of a substation and a telephone line.

lhe particular substation herein illustrated and described is amodification of a general type described in U. S. Patent 1,254,471issued to George A. Campbell, January 22, 1918, and particularly theform shown in Figs. 4 and 4A of the said patent,

As stated in the patent to Campbell referred to above, telephonesubstations of the type therein disclosed comprise a transmit ter, areceiver, a balancing network consisting in the simplest form or anauxiliary resistance and a transformer having a plurality of windingswhich, in combination with a telephone line are so designed that (l) thetransmitter and receiver shall be conjugate, that is, there shall benegligible side tone in the receiver in consequence of the actuation ofthe transmitter by sound waves; (2) the line and auxiliary resistanceshall be conjugate in order that a negligible amount of the energyabsorbed by the substation :trorn the line shall be wasted in saidauxiliary resistance; (3) for a given line having a definite impedance,the telephonic energy delivered by the transmitter shall be a maximum;{i the amount of energy delivered by the line to the substation shall bea maximum, in other words, the impedance of the substation as seen fromthe line shall be numerically equal to the impedance of the line; (5) ata small sacrifice of eiiiciency it shall be possi-= ble to discriminateefi'ectively against disturbing line noise as distinguished from thetelephonic signals from the communicating station.

A substation satisfying the above men tioned requirements is ideal inthat its overall efiiciency from the transmitter of one station to thereceiver of the communicating substation is the theroretical maximumwhich cannot be exceeded by any two similar invariable substationswhether satisfying the requirement of transmitter and receiver conjugacyor not. It is further ideal in that a minimum number of elements isemployed since at least one auxiliary ele ment is necessary to securefreedom from side tone.

It is an object of the present invention to adapt a circuit of thegeneral type mentioned above to particular system requirements witheconomy of parts and simplification of wiring and assembly. r

In the case of a. common battery, anti-side tone substation circuit, itis desirable from a transmission standpoint that the capacity of thecondenser, which is necessary to maintain all direct current from theline through the transmitter, be larger than the capacity of thecondenser which is connected in series with the ringer. This requirementmeans that two condensers must be employed in the substation circuit,

In the case of a substation it is usual to provide a box which iscommonly called a subset and in which is housed the ringer, theinduction coil or transformer and the balancing network. ed b means of acord having a pluralit of con actors to adeslr stand or handset w ichcomprises the switchhook, receiver, and transmitter, and in the case ofdial systems also includes the dial.

The invention provides a circuit in which these features are present andin which a minimum number of conductors is used for connecting thesubscribers set to the handset or desk stand.

Another object of the invention is the pro vision oi means fordecreasing interference effects on neighboring electrical circuits (e.g. radio sets) caused by the pulsations trans lhis subset is connectmitted over the line when a dial is operated V at the substation. a

@ther and further obJects of the invention will be clear from thefollowing description Fig. 2 is a diagram showing the circuit of Fig. 1in greater detail;

ig. 3 is a practical arrangement of a substation fundamentally like t atof Fig. 2 in l which a so-called desk stand or wall set equipped with adial is used;

Fig. 4 is a practical arrangement of a sub station fundamentally likethat of Fig. 2 in a which a so-called hand set equipped with a dial isused;

Fig. 5 is a modification of the desk stand or wal set circuitconnections shown in Fig. 3;

Fig. 6 is a modification of the hand set cirsuit connection shown inFig. 4.

Referring to Figs. 1 and 1-A, a telephone line L is connected to asubstation comprisin a transmitter T, a receiver R, and a threewindintransformer having two low resistance windings 11 and 12 and a highresistance winding 13 (which may include an auxiliary resistance X),said windings being on a common core and preferably having very smallleakage.

mitter T, receiver R, high resistance winding 13 and low resistancewinding 11 are connected together at a common point 14. The otherterminal of the low resistance winding 11 is connected to one side ofthe line L at 15,

the other terminal of the receiver R and the other terminal of the highresistance winding 13 (when the auxiliary resistance X is part of thewinding 13) are connected togather and to one terminal of the lowresistance winding 12 at 16. The other terminal of the low resistancewinding 12 is connec to the other terminal of the transmitter T and theother side of the line at 17. When it is desired to exclude the batterysupply current from the receiver R and winding 12, a condenser 18 may beinserted preferably be" tween the winding 12 and the connection of thetransmitter T and the line L at 17.

The theory of operation of the fundamental t of substation shown inFigs. 1 and 1-A is the same as that described for Figs. 4, 4a, 5 and 6in the above-mentioned Campbell Patent 1,254,471 except that the factthat the low resistance winding 11 has been placed in the opposite sideof the line must be taken into consideration. This low resistancewinding 11, when located as shown in Fi s. 1 and 1-A simplifies theconstruction of t e induction coil in that it can be made with but fourexternal connections and also simplifies the switchhook and cordingarrangements which can be used with the circuit.

Fi 2 shows the circuit of Fig. 1 to which has n added a switchhook 19,contacts 20 and 21 and a pair of contacts 22. When the receiver R isremoved from the switchhook 19, the contacts 20 and 21 are in contactwith the switchhook 19 and the pair of contacts 22 are closed as shown.Placing the receiver R on the switchhook 19 opens the nor- One terminalof the trans-.

ted A---A mally closed contacts 22 thereby opening the circuit from theline L through the condenser 18, windin 12, auxiliary resistance X,winding 13 an winding 11, and also opens the circuit of the transmitterT and receiver R. A callin device 23 is bridged across the line L inseries with denser preferably has a. capacity between mi. and 1 11115.

An induction coil which has been found satisfactory for this type waswound on a spool and mounted on a closed core of laminated siliconsteel. The inner winding 11 comprised approximately 940 turns having aresistance of approximately 24 ohms, the inner terminal being arrangedto be connected to the line L at 15 and the outer terminal connected tothe inner end oi the middle winding 13 at 14. The middle winding 13 andthe auxiliary resistance X comprise approximately-245 turns having aresistance of approximately 50 ohms, the outer terminal being arrangedto he connected to the inner terminal of the outer winding 12 at 18. Theoumr winding 12 comprises approximately 565 turns having'a resistance ofapproximately 21 ohms. The middle winding 13;. was wound in an oppositedirection to that 01'' the inner winding 11 and the outer winding 12. Acondenser having a capacity of approximately 2 mi. has been foundsatisfactory for the condenser 18.

The substation in Fig. 3 comprises a socalled subscribers s t (shownabove the line and a so-called desk stand (shown below the line B-B).The subscribers set, and desk stand are connected together by means of acord. The subscrihers set houses the signaling device 23 with itsassociate condenser 24 and the induction coil of the type describedabove in connection with Fig.

2 and its associated condenser 18. It is connected to the line L andprovided with five terminals- 25, 26, 27, 28 and 29 in addition to theline terminals." The desk stand comprises the receiver R, transmitter T,switchhook 19 with its associated contacts and 21 and pair of contacts22 and a dial DL, preferably of the type described in U. S. Patent1,353,612 to Reeves, September 21, 1920. The desk stand is provided withfour terminals 36, 37, 38 and 39. The terminals 26, 27, 28 and 29 of thesubscribers set are connected to the terminals 36, 37 ,38 and 39 of thedesk stand respectively by means of a four conductor cord. The terminalof the subscribers set is not used when the subscribers set is connectedto a desk stand of the typeshown in Fig. 3 and its use will be describedlater in connection with Fig. 5. A condenser 30, the capacity of whichis relatively small, is connected in shunt to the winding 11 of theinduction coil when desired. This condenser reduces the interferacondenser 24. This con of subscribers set once on neighboring radio setscaused by the pulsations transmitted over the line from the substationwhen the dial BL is operated.

The subststion in Fig. 4 is similar to that of Fig. 3 except that ecombined transmitter and receiver TR with its associated cradle contactswitching mechanism of a type well known in the art a we employed.

The desk stand in Fig. 5 is in general similer to that of Fig. 8. It isprovided with five terminals 55, 56, 5?, 58 end 59 which are connected(not shown) to terminels 25, 26, 2?, 28 end 29 respectively of thesubscribers set of Fig. 3 by means of a five conductor cord. Theswitcblioclz contacting arrangement and the dialing contect arrangementhave been modified so that the Winding l1 will be included in the pathwhich short-circuits the tiensinittei" T when the dial BL is operated totransmit dialing impulses over the iine. This sliort-circuiting potiimay be traced from the transmitter T, terminal 56, cord conductor toterminal 28, coil 11 at 1%. the other terminal of coil 11 st 15,terminal 25, cord conductor to terminates, diel contect 51, totransmitter 'l. This elicit-circuiting of the winding 11 dosing dialinghas been found to reduce the interierence efiects on neighboring radiosets csused by the opera.- tion of the dial. With 8. desis stood of thetype shown in Fig. 5, the condenser 39 connected across the winding 11on the induction coil may be omitted The bond set in ois in generalsimiiei' to that of 4:. it is provided with five terminals $6, 6?, 68,69and 7% which connected (not shown} to terminels 25, 26, 27, 28 end 23i'espectively oi the subscriber set of 4 by means of s five conductorcord. Provision is made in the circuit srrsngemerit for the bend sets ofFig. 6 to include the winding 11 oi the induction coil in theshortcircuiting path for the transmitter during dialing in e mannersimilsi' to tiiet employed in the desk stead of Fig. 5.

The invention is slso capable of other modificstions end adaptations notspecifically re- Iierrcd to but included within the scope of theepuended claims.

Wbet is claimed l. A signeling circuit including in series fourcomponents, the first of said components including o iine, the secondoi? ssid components including a winding of e trensicrmer, the third ofsaid components including o. receiving instrument in persllel with eseries errengement of e lie-lensing impedence means end e second windingof said trensiormer, the fourth of seid components including a thirdwinding of said trensiormer, e. tronsmitting instrument connected inshunt with a series connection "of said first end second components,said three windings being termineted on four terminals and having acommon magnetic field, s contact common to said transmitting instrument,said receiving instrument and two of said transformer windings, a shuntcircuit for said transmltting instrument, an impulse sending device andcontacts controlled by said device for opening the circuit of saidreceiving instru ment and closing the shunt circuit whenever said deviceis moved from normal.

2. A signaling circuit including in series four components, the first ofsaid components including a line, the second of said componentsincluding a winding of a transformer, the third of said componentsincluding a receiving instrument in parallel with a series arrangementof a balancing impedance means and a second winding of said transformer,the fourth of said components including o: third winding of saidtronsformer, a transmitting instrument connected in shunt with a seriesconnection of said first and second components, said three transformerwindings being terminated on the four terminals, 21 contact common tosaid transmitting instrument, said receiving instrument said secondwinding and said third winding, normally open circuits for saidtransmitting instrument and said receiving instrument and said line, andmeans for closing said circuits.

3. A telephone system adopted for use with a common buttery systemincluding in series our components, the first of said componentsincluding a, line, the second of said components including a winding ofa transformer, the third or" said components including a receivinginstrument in parallel with a, series arrangement of s balancingimpedance means and a second winding of: said transformer, the fourth ofsaid components including a third winding of said transformer, atransmitting instrument connected in shunt with the series connection ofsaid first and second components, said three teensiormer windings beingterminated on four terminals, e contact common to said trons mittinginstrument, said receiving instrument, said second winding and saidthird winding, normally open circuits for said re ceiving instrument andsaid transmitting instrument, means for closing said circuits, animpulse sending device, means actuated by said device for transmittingimpulses, end mesns actuated during the operation of said sending devicefor opening the receiving instrument circuit and shunting the transmitting instrument circuit and one of the windings of said transformer.

4-. A signaling circuit comprising a. tronsformer, a path for thetransmission end reception of signals, a path including o transmittingapparatus, a path including 3. winding of a transformer, a resistanceend a. receiver, said receiver being included in a path shunted aboutsaid winding of said trons former and said resistance, said lastmenill!) tioned path and a second winding of said transformer beingincluded in a series circuit, said series circuit being shunted aboutsaid transmitting apparatus, said first mentioned path and a thirdwinding of said transformer being included in a series cit cuit shuntedabout said transmitting apparatus, said three transformer windings hemterminated on four terminals, said thir winding of said transformer,said receiver, said transmitting apparatus and said first mentionedwinding of said transformer having a common contact with respect toalternating signaling current.

5. In a two-way signaling system, a circuit for the transmission andreception of signals, a normally open transmitting circuit proper, anormally open receiving circuit proper, a balancing circuit, atransformer with three windings terminated on four terminals, saidelements being so proportioned and related that said receiving circuitand said transmitting circuit proper are conjugate, contacts actuated bya switchhook for closing said normally open transmitting and receivingcircuits, a receiving instrument in said receiving circuit, saidreceiving instrument being connected, through switchhook contacts, froma point common to two of said windingsto a point common to a difierentpair of said windings.

6. A circuit according to claim 1 in which said transmitter, receiver,contacts and impulse sendingdevice are grouped together and separatedfrom said transformer, and a fourconductor cord interconnects theelements so grouped and the windings of said trans former.

In witness whereof, I hereunto subscribe my name this 27th da of Februar1931.

, JOHN iv. eoonnhnm

